Re: [Qemu-devel] alt-gr on Windows

[Stefan Weil <sw@weilnetz.de>]

Am 01.01.2015 um 17:24 schrieb Andreas Färber:
> Hi, Am 18.12.2014 um 12:55 schrieb Kevin Wolf:
>> Am 17.12.2014 um 01:11 hat Thebault, Remi geschrieben:
>>> This is not the first post on this topic, but I haven't seen any 
>>> solution about it. I tested so far linux guest on windows host and 
>>> the AltGr key is dead in the guest. (using git master branch) On 
>>> french keyboard, the keys to yield the bar "|" are alt-gr + 6. when 
>>> executing this combination on keyboard, Windows generates this: - 
>>> L-CTRL - R-ALT - 6 in Qemu (only digged gtk UI so far), pressing 
>>> alt-gr + 6 generates the following trace - L-CTRL - L-ALT <-- note 
>>> left here - 6 This comes from the Win32 call MapVirtualKey in gtk.c 
>>> that maps to scancodes without left/right distinction. Even when 
>>> sending the right alt to the guest, the alt-gr key remains dead 
>>> because of ctrl being virtually pressed. I found out however that if 
>>> R-ALT + 6 is sent without the ctrl key, the guest finally recognize 
>>> it and prints the bar, @, # and other [}{]. To make things easier, 
>>> Windows delivers the ctrl code before the alt code, so catching it 
>>> cleanly before delivery to the guest is probably tough. I could 
>>> however come to an easy and quick fix with sending the "ctrl up" 
>>> signal to the guest before the "r-alt down" is sent. My current code 
>>> do not handle all corner cases (eg: turbo mode) and only fixes the 
>>> gtk ui, but would such fix be accepted in the repo? Would this break 
>>> somehow the windows guest on windows host? 
>> CCing Stefan Weil, who is both the Windows maintainer and the author 
>> of commit 2777ccc5, which introduced the MapVirtualKey() call. As 
>> there is a special case for Alt Gr in the code, I suppose he had this 
>> working back then. From what I understand (which isn't much when it's 
>> about Windows), it seems very unlikely to me that the change would 
>> break anything that is working today; but you should probably give it 
>> some testing before posting a patch. 
> Tim and colleagues have been investigating some AltGr issues on Linux 
> / NoVNC as well, so it may well have been broken before Stefan's 
> commit. Regards, Andreas 


Indeed, when I wrote that commit, it fixed an AltGr issue. I spent the 
last weeks (well, not all the time, but some minutes) to restore my 
previous test scenario, but without success.

Remi's patch is a clear improvement of the current situation, but the 
problem is more complicated than one would think at a first glance.

I suggest calling MapVirtualKey only for those keys which don't need 
special handling, so it would be in the default case of the switch 
statement.

It looks like Alt-Ctrl is a valid alternative for pressing AltGr on 
Windows, so we have to take that into account, too.

Wine also needs special handling because it sends a single (different) 
key code instead of two key codes.

Regards
Stefan